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authorJiang Liu <liuj97@gmail.com>2013-07-04 02:03:14 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-04 03:07:33 +0400
commitc3d5f5f0c2bc4eabeaf49f1a21e1aeb965246cd2 (patch)
treeec3b59b33102150b20c04de0b43d25dcea692b68 /include
parent7b4b2a0d6c8500350784beb83a6a55e60ea3bea3 (diff)
downloadlinux-c3d5f5f0c2bc4eabeaf49f1a21e1aeb965246cd2.tar.xz
mm: use a dedicated lock to protect totalram_pages and zone->managed_pages
Currently lock_memory_hotplug()/unlock_memory_hotplug() are used to protect totalram_pages and zone->managed_pages. Other than the memory hotplug driver, totalram_pages and zone->managed_pages may also be modified at runtime by other drivers, such as Xen balloon, virtio_balloon etc. For those cases, memory hotplug lock is a little too heavy, so introduce a dedicated lock to protect totalram_pages and zone->managed_pages. Now we have a simplified locking rules totalram_pages and zone->managed_pages as: 1) no locking for read accesses because they are unsigned long. 2) no locking for write accesses at boot time in single-threaded context. 3) serialize write accesses at runtime by acquiring the dedicated managed_page_count_lock. Also adjust zone->managed_pages when freeing reserved pages into the buddy system, to keep totalram_pages and zone->managed_pages in consistence. [akpm@linux-foundation.org: don't export adjust_managed_page_count to modules (for now)] Signed-off-by: Jiang Liu <jiang.liu@huawei.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Michel Lespinasse <walken@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: <sworddragon2@aol.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: David Howells <dhowells@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Joonsoo Kim <js1304@gmail.com> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Tang Chen <tangchen@cn.fujitsu.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wen Congyang <wency@cn.fujitsu.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mm.h6
-rw-r--r--include/linux/mmzone.h14
2 files changed, 12 insertions, 8 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 083cc0ba2384..4310f80ce956 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1313,6 +1313,7 @@ extern void free_initmem(void);
*/
extern unsigned long free_reserved_area(void *start, void *end,
int poison, char *s);
+
#ifdef CONFIG_HIGHMEM
/*
* Free a highmem page into the buddy system, adjusting totalhigh_pages
@@ -1321,10 +1322,7 @@ extern unsigned long free_reserved_area(void *start, void *end,
extern void free_highmem_page(struct page *page);
#endif
-static inline void adjust_managed_page_count(struct page *page, long count)
-{
- totalram_pages += count;
-}
+extern void adjust_managed_page_count(struct page *page, long count);
/* Free the reserved page into the buddy system, so it gets managed. */
static inline void __free_reserved_page(struct page *page)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e511f9429f1e..09d381b71fd8 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -474,10 +474,16 @@ struct zone {
* frequently read in proximity to zone->lock. It's good to
* give them a chance of being in the same cacheline.
*
- * Write access to present_pages and managed_pages at runtime should
- * be protected by lock_memory_hotplug()/unlock_memory_hotplug().
- * Any reader who can't tolerant drift of present_pages and
- * managed_pages should hold memory hotplug lock to get a stable value.
+ * Write access to present_pages at runtime should be protected by
+ * lock_memory_hotplug()/unlock_memory_hotplug(). Any reader who can't
+ * tolerant drift of present_pages should hold memory hotplug lock to
+ * get a stable value.
+ *
+ * Read access to managed_pages should be safe because it's unsigned
+ * long. Write access to zone->managed_pages and totalram_pages are
+ * protected by managed_page_count_lock at runtime. Idealy only
+ * adjust_managed_page_count() should be used instead of directly
+ * touching zone->managed_pages and totalram_pages.
*/
unsigned long spanned_pages;
unsigned long present_pages;